Pension and Savings Plans - Change in Benefit Obligation, Plan Assets and Funded Status of Pension Plans (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Change in benefit obligation:
Projected benefit obligation at beginning of period	$ 139.5
Projected benefit obligation at end of period	139.5
Amounts recognized in the consolidated balance sheets:
Noncurrent asset (included in “Investments and other assets”)	28.5	$ 39.6
Pension Plan
Change in benefit obligation:
Projected benefit obligation at beginning of period	751.7	816.4	$ 853.8
Service cost	0.2	0.3	2.0
Interest cost	20.4	28.0	33.5
Benefits paid and administrative fees (net of Medicare Part D reimbursements)	(55.9)	(57.5)
Actuarial (gain) loss	(29.4)	43.4
Settlement	0.0	(51.6)
Projected benefit obligation at end of period	751.7	816.4	853.8
Funded status at end of period	20.7	31.1
Change in plan assets:
Fair value of plan assets at beginning of period	847.5	855.2
Actual return on plan assets	(19.2)	101.4
Benefits paid	(55.9)	(57.5)
Settlement	0.0	(51.6)
Fair value of plan assets at end of period	772.4	847.5	$ 855.2
Amounts recognized in the consolidated balance sheets:
Noncurrent obligation (included in Other noncurrent liabilities)	(7.8)	(8.5)
Net amount recognized	$ 20.7	$ 31.1

Amount of increase (decrease) in plan assets of defined benefit plan from actual return (loss) determined by change in fair value of plan assets adjusted for contributions, benefit payments, and other expenses.

Name:	us-gaap_DefinedBenefitPlanActualReturnOnPlanAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of gain (loss) from change in actuarial assumptions which (increases) decreases benefit obligation of defined benefit plan. Assumptions include, but are not limited to, interest, mortality, employee turnover, salary, and temporary deviation from substantive plan.